Molecular Test Helps ID Three Types of Vaginal Infections

High sensitivity, specificity vs gold standard testing methods

A molecular-based test to diagnose three common vaginal infections performed with a high sensitivity and specificity when using both clinician and patient-collected samples, researchers found.

This investigational, FDA-approved nucleic acid test detected bacterial vaginosis, vaginal candidiasis, and trichomoniasis with at least 80%-90% sensitivity and specificity, which was comparable to the gold standard methods of diagnosing these infections, reported Charlotte Gaydos, MS, of Johns Hopkins University, and colleagues.

They published their work in Obstetrics and Gynecology, having previously presented it at a variety of conferences, including ASM Microbe, the American College of Obstetricians and Gynecologists annual conference, and the American Molecular Pathology meeting.

In a podcast, Nancy Chescheir, MD, the journal's editor-in-chief, said that while this was an industry-sponsored study, she still characterized it as "well-done" and that it "used principles of good practice."

"This will improve the care of patients, although the study doesn't talk about costs and workflow issues," Chescheir said. "Those kinds of details would need to be worked out before a hospital or clinic setting would probably purchase this."

Gaydos and colleagues conducted a multicenter cross-sectional study in 10 clinical centers where patients collected their own vaginal swabs in addition to clinician-collected swabs. Overall, swabs were collected from 1,740 patients and evaluated via molecular test and six reference tests -- two per infection. About half of patients were black and a quarter were white, with over 90% with a high school education or above. Half of patients had a single sexual partner or no sexual partner over the past year.

Examining diagnoses, bacterial vaginosis was diagnosed in 56.5%, vaginal candidiasis in 32.8% and trichomoniasis in 8%, with none of the infections in 24%, with a co-infection rate of 20%.

Overall, the respective sensitivity and specificity of the investigational tests for swabs collected by clinicians were:

Bacterial vaginosis: 90.5%, 85.8%

Candida group: 90.9%, 94.1%

Trichomonas vaginalis: 93.1%, 99.3%

Very similar results were obtained with patient-collected swabs, with sensitivity and specificity as follows:

Bacterial vaginosis: 90.7%, 84.5%

Candida group: 92.2%, 91.9%

T. vaginalis: 93.2%, 99.3%

The authors said that the performance of this test was "similar to other FDA nucleic acid amplification test-cleared assays." They pointed to research that suggested "more complex processes" may be necessary to diagnose bacterial vaginoses, because many organisms "can only be detected by amplification tests." Notably, these tests may be able to detect the decreased presence of certain Lactobacillus species, which are present in normal vaginal flora and decreased or lost in bacterial vaginosis, they said.

"A molecular assay based on the presence of lactobacilli and the absence of deleterious organisms represents an opportunity to improve the diagnosis of bacterial vaginosis," they wrote.

Chescheir agreed that a global acceptance of these kinds of tests -- not just this one specific test -- "seem to push the bar up on our ability to identify the source of a patient's vaginitis symptoms."

"I guess this is the direction we're going. If it makes that easier, that's terrific," she said.

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